Imagine this: You step into a vast department store to buy a new blender, and your smartphone leads you straight to the right aisle, and then lights up with a coupon for the KitchenAid model to your left.

The one remaining on the shelf has already been opened, so using your phone again, you summon a store clerk who finds a fresh box out back. Then you quickly pay with a wave of your phone over a small, glowing box that serves as a checkout register, which automatically adds points to your rewards account.

Welcome to the future of brick-and-mortar shopping, made possible by a GPS-like technology that works inside buildings and is made by Boston tech start-up ByteLight. But instead of beams from satellites that can’t penetrate walls, ByteLight uses LED light bulbs, now in so many stores, to transmit data via their pulsing light waves to the camera in a smartphone.

“The opportunity for indoor location is enormous,” said ByteLight chief executive Dan Ryan. “Right now, it’s a bit of a Wild West scenario, in that there’s a million different technologies that are trying to figure out a solution for this. Nobody’s quite gotten there yet, but we think there’s going to be an incredible opportunity.”

Indeed, indoor location technology is a huge emerging field with stiff competition and many of the biggest names in the business. Google Inc. has designed its maps application to help Android users navigate through more than 10,000 buildings worldwide — including airports, shopping malls, museums, and college campuses.

The In-Location Alliance, a collaborative effort by mobile giants Nokia, Samsung, and Sony, and 19 smaller companies, is working on an indoor navigation system that determines a user’s position via Wi-Fi and Bluetooth, by triangulating distances between hotspots and mobile handsets.

And Apple joined the fray in March when it bought indoor location start-up WiFiSlam for $20 million.

Indoor location tracking has too many potential applications to count, Ryan said, but ByteLight is focused for now on the retail industry.

“What they lack,” Ryan said of ByteLight’s rivals, “is the ability to put a dot on the map that’s accurate, and that’s the piece that ByteLight fills in.”

Google says it can pinpoint a user’s location within several meters. Apple’s newly acquired WiFiSlam is accurate to about 8 feet. ByteLight says its margin of error is less than a meter.

Several large retailers are testing ByteLight’s navigation technology as a tool for improving employee efficiency, but customers are not yet using the system, Ryan said. He declined to name the companies.

Further along is the glowing box — ByteLight’s light field communication device, which is designed to outperform the much-hyped near field communication, which uses radio signals to perform tasks such as contactless payments within stores. But near field communication is unsupported by many mobile devices, including Apple’s iPhone, whose aluminum backing blocks radio frequencies.

By contrast the ByteLight box uses light waves for such transactions, and is compatible with every camera-equipped smartphone. The company says its glowing box will make its commercial debut Wednesday at 100 retail locations in Shanghai.

Ryan and cofounder Aaron Ganick began thinking seriously about LED data transmission as undergraduates at Boston University, where they worked at the school’s Smart Lighting Engineering Research Center.

“This entire world is shifting over to LEDs,” Ryan said. “So you’re going to have this enormous infrastructure that’s deployed across every single building in the entire world. What can we do with that? What opportunities become enabled?”

The pair figured out a way to manipulate the pulsing light waves emitted by LED bulbs so they send data as they flicker. Using microchips mounted to the bulbs, the ByteLight technology causes the LED bulbs to flicker very fast — too fast for the naked eye to see — and, in doing so, to communicate information to a smartphone through its camera lens. The communication between light bulb and smartphone enables shoppers using a retailer’s mobile application to navigate through a store, receive special offers on the products in front of them, or be located by a sales representative.

Ryan said the duo realized after some experimentation that “LEDs’ digital nature means that you can switch [the lights] on and off so fast that you can transmit a data signal to a user indoors.”

Ryan and Ganick devoted themselves full time to ByteLight in 2011, a year after graduation, when they were accepted by the Summer@Highland accelerator program hosted by Highland Capital Partners in Cambridge. Last year, the company announced $1.25 million in seed funding, led by VantagePoint Capital Partners of San Bruno, Calif.

Indoor location tracking has too many potential applications to count, Ryan said, but ByteLight is focused for now on the retail industry.

“At some level, it allows retail to really return to its roots,” Ryan said. “The origins of retail were general stores. You went down to the local store, the owner knew your name, knew what you liked. That aspect was lost as we transitioned to this big box model of retail. Now, when you combine indoor location with mobile phones, you can customize the shopping experience.”

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